Memory device, semiconductor device, method for producing memory device, and method for producing semiconductor device

ABSTRACT

A semiconductor device includes a first pillar-shaped semiconductor layer and a gate insulating film around the first pillar-shaped semiconductor layer. A gate electrode is around the gate insulating film and a gate line is connected to the gate electrode. A first diffusion layer resides in an upper portion of the first pillar-shaped semiconductor layer and a second diffusion layer resides in a lower portion of the first pillar-shaped semiconductor layer. A memory device on the first diffusion layer includes a pillar-shaped phase-change layer and a reset gate insulating film surrounding the pillar-shaped phase-change layer. A reset gate surrounds the reset gate insulating film, where the reset gate functions as a heater, and the pillar-shaped phase-change layer and the reset gate are electrically insulated from each other.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/483,791, filed Sep. 11, 2014, which is a continuation ofPCT/JP2013/080148 filed on Nov. 7, 2013. The entire contents of whichare incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a semiconductor memory device.

BACKGROUND ART

In recent years, phase-change memories have been developing (refer to,for example, PTL 1). In phase-change memories, information is memorizedby changing and recording the resistance of an information memoryelement of a memory cell.

The mechanism is as follows. When a current is allowed to flow between abit line and a source line by turning a cell transistor to the on-state,heat is generated in a heater, which is a high-resistance element.Chalcogenide glass (GST: Ge₂Sb₂Te₅) that contacts this heater is melted,thereby causing a transition of the state of the chalcogenide glass.When the chalcogenide glass is melted at a high temperature (bysupplying a high current) and cooled at a high speed (by stopping thecurrent), the chalcogenide glass transitions to an amorphous state(reset operation). When the chalcogenide glass is melted at a relativelylow high-temperature (by applying a low current) and slowly cooled (bygradually decreasing the current), the chalcogenide glass iscrystallized (set operation). With this mechanism, at the time ofreading out information, information of “0” or information of “1” isdetermined on the basis of the case where the amount of current flowingbetween the bit line and the source line is large (lowresistance=crystal state) and the case where the current flowing betweenthe bit line and the source line is small (high resistance=amorphous)(refer to, for example, PTL 1).

In this case, for example, the reset current is very large, namely, 200μA. In order to make the reset current large in this manner and to allowthis current to flow to a cell transistor, the size of a memory cell hasto be very large. In order to allow a large current to flow, a selectionelement such as a bipolar transistor or a diode can be used (refer to,for example, PTL 1).

Diodes are two-terminal elements. Therefore, in order to select a memorycell, when one source line is selected, currents of all memory cellsconnected to the one source line flow in the one source line.Consequently, the IR drop in the resistance of the source lineincreases.

On the other hand, bipolar transistors are three-terminal elements.However, since a current flows in a gate, it is difficult to connect alarge number of transistors to a word line.

A surrounding gate transistor (hereinafter referred to as “SGT”) havinga structure in which a source, a gate, and a drain are arranged in adirection perpendicular to a substrate and a gate electrode surrounds apillar-shaped semiconductor layer has been proposed (refer to, forexample, PTL 2). Since the source, the gate, and the drain are arrangedin a direction perpendicular to the substrate, a small cell area can berealized.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2012-204404

PTL 2: Japanese Unexamined Patent Application Publication No.2004-356314

SUMMARY

Accordingly, an object is to provide a memory including a memory devicewhich includes a layer whose resistance changes and in which reset canbe performed by using a reset gate.

A memory device of the present invention includes a pillar-shaped layerwhose resistance changes, a reset gate insulating film surrounding thepillar-shaped layer whose resistance changes, and a reset gatesurrounding the reset gate insulating film.

The memory device may include a lower electrode under the pillar-shapedlayer whose resistance changes.

The reset gate may be composed of titanium nitride.

The reset gate insulating film may be formed of a nitride film.

The lower electrode may be composed of titanium nitride.

The layer whose resistance changes may be reset by allowing a current toflow in the reset gate.

A semiconductor device includes a first pillar-shaped semiconductorlayer, a gate insulating film formed around the first pillar-shapedsemiconductor layer, a gate electrode formed around the gate insulatingfilm, a gate line connected to the gate electrode, a first diffusionlayer formed in an upper portion of the first pillar-shapedsemiconductor layer, a second diffusion layer formed in a lower portionof the first pillar-shaped semiconductor layer, and the above-describedmemory device formed on the first diffusion layer.

The semiconductor device may include a fin-shaped semiconductor layerformed on a semiconductor substrate, a first insulating film formedaround the fin-shaped semiconductor layer, the first pillar-shapedsemiconductor layer formed on the fin-shaped semiconductor layer, andthe gate insulating film formed on a periphery and a bottom portion ofthe gate electrode and the gate line. The gate electrode may be composedof a metal, the gate line may be composed of a metal, the gate line mayextend in a direction perpendicular to a direction in which thefin-shaped semiconductor layer extends, and the second diffusion layermay be further formed in the fin-shaped semiconductor layer.

The second diffusion layer may be further formed in the semiconductorsubstrate.

The semiconductor device may include a contact line that is parallel tothe gate line and connected to the second diffusion layer.

The semiconductor device may include the fin-shaped semiconductor layerformed on the semiconductor substrate, the first insulating film formedaround the fin-shaped semiconductor layer, a second pillar-shapedsemiconductor layer formed on the fin-shaped semiconductor layer, acontact electrode formed around the second pillar-shaped semiconductorlayer and composed of a metal, the contact line connected to the contactelectrode and composed of a metal extending in a direction perpendicularto the direction in which the fin-shaped semiconductor layer extends,and the second diffusion layer formed in the fin-shaped semiconductorlayer and in a lower portion of the second pillar-shaped semiconductorlayer. The contact electrode may be connected to the second diffusionlayer.

An outer width of the gate electrode may be the same as a width of thegate line, and a width of the first pillar-shaped semiconductor layer inthe direction perpendicular to the direction in which the fin-shapedsemiconductor layer extends may be the same as a width of the fin-shapedsemiconductor layer in the direction perpendicular to the direction inwhich the fin-shaped semiconductor layer extends.

The semiconductor device may include the gate insulating film formedbetween the second pillar-shaped semiconductor layer and the contactelectrode.

A width of the second pillar-shaped semiconductor layer in the directionperpendicular to the direction in which the fin-shaped semiconductorlayer extends may be the same as the width of the fin-shapedsemiconductor layer in the direction perpendicular to the direction inwhich the fin-shaped semiconductor layer extends.

The semiconductor device may include the gate insulating film formed ona periphery of the contact electrode and the contact line.

An outer width of the contact electrode may be the same as a width ofthe contact line.

The semiconductor device may include the first pillar-shapedsemiconductor layer formed on a semiconductor substrate, and the gateinsulating film formed on a periphery and a bottom portion of the gateelectrode and the gate line. The gate electrode may be composed of ametal, the gate line may be composed of a metal, and the seconddiffusion layer may be further formed in the semiconductor substrate.

A method for producing a memory device according to the presentinvention includes a sixth step of forming a pillar-shaped layer whoseresistance changes and a lower electrode on a semiconductor substrate,forming a reset gate insulating film so as to surround the pillar-shapedlayer whose resistance changes and the lower electrode, and forming areset gate.

A method for producing a semiconductor device includes a first step offorming a fin-shaped semiconductor layer on a semiconductor substrateand forming a first insulating film around the fin-shaped semiconductorlayer; a second step of, after the first step, forming a secondinsulating film around the fin-shaped semiconductor layer, depositing afirst polysilicon on the second insulating film and planarizing thefirst polysilicon, forming a second resist for forming a gate line, afirst pillar-shaped semiconductor layer, a second pillar-shapedsemiconductor layer, and a contact line in a direction perpendicular toa direction in which the fin-shaped semiconductor layer extends, andetching the first polysilicon, the second insulating film, and thefin-shaped semiconductor layer to thereby form a first pillar-shapedsemiconductor layer, a first dummy gate composed of the firstpolysilicon, a second pillar-shaped semiconductor layer, and a seconddummy gate composed of the first polysilicon; a third step of, after thesecond step, forming a fourth insulating film around the firstpillar-shaped semiconductor layer, the second pillar-shapedsemiconductor layer, the first dummy gate, and the second dummy gate,depositing a second polysilicon around the fourth insulating film, andleaving, by conducting etching, the second polysilicon on side walls ofthe first dummy gate, the first pillar-shaped semiconductor layer, thesecond dummy gate, and the second pillar-shaped semiconductor layer toform a third dummy gate and a fourth dummy gate; a fourth step offorming a second diffusion layer in an upper portion of the fin-shapedsemiconductor layer, in a lower portion of the first pillar-shapedsemiconductor layer, and in a lower portion of the second pillar-shapedsemiconductor layer, forming a fifth insulating film around the thirddummy gate and the fourth dummy gate, leaving the fifth insulating filmin a side wall shape by etching to form side walls formed of the fifthinsulating film, and forming a compound of a metal and a semiconductorin an upper portion of the second diffusion layer; a fifth step of,after the fourth step, depositing an interlayer insulating film andplanarizing the interlayer insulating film to expose upper portions ofthe first dummy gate, the second dummy gate, the third dummy gate, andthe fourth dummy gate, removing the first dummy gate, the second dummygate, the third dummy gate, and the fourth dummy gate, removing thesecond insulating film and the fourth insulating film, forming a gateinsulating film around the first pillar-shaped semiconductor layer,around the second pillar-shaped semiconductor layer, and on an innerside of the fifth insulating film, forming a fourth resist for removinga portion of the gate insulating film which is located on a periphery ofa bottom portion of the second pillar-shaped semiconductor layer,removing the portion of the gate insulating film which is located on theperiphery of the bottom portion of the second pillar-shapedsemiconductor layer, depositing a metal and etching back the metal toform a gate electrode and a gate line around the first pillar-shapedsemiconductor layer and to form a contact electrode and a contact linearound the second pillar-shaped semiconductor layer; after the fifthstep, depositing a second interlayer insulating film and planarizing thesecond interlayer insulating film to expose an upper portion of thefirst pillar-shaped semiconductor layer; and the sixth step describedabove.

The method for producing a semiconductor device may further include,after depositing the first polysilicon on the second insulating film andplanarizing the first polysilicon, forming a third insulating film onthe first polysilicon.

A fourth insulating film may be formed around the first pillar-shapedsemiconductor layer, the first dummy gate, the second pillar-shapedsemiconductor layer, and the second dummy gate. A third resist may thenbe formed and etch-back is performed to expose an upper portion of thefirst pillar-shaped semiconductor layer, and a first diffusion layer maybe formed in the upper portion of the first pillar-shaped semiconductorlayer. According to the present invention, it is possible to provide amemory including a memory device which includes a layer whose resistancechanges and in which reset can be performed by using a reset gate.

The memory device includes a pillar-shaped layer whose resistancechanges, a reset gate insulating film surrounding the pillar-shapedlayer whose resistance changes, and a reset gate surrounding the resetgate insulating film. With this structure, when a current is supplied tothe reset gate, heat is generated in the reset gate functioning as aheater. Consequently, chalcogenide glass (GST: Ge₂Sb₂Te₅) that contactsthis heater is melted, and a transition of the state of the chalcogenideglass can be caused.

The memory device has the structure in which the reset gate surroundsthe pillar-shaped layer whose resistance changes, and thus thepillar-shaped layer whose resistance changes is easily heated.

Since the reset is performed by allowing a current to flow in the resetgate, a large current need not be supplied to a selection element and itis sufficient that a low current for a set operation can be allowed toflow in the selection element.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a bird's-eye view of a memory device according to the presentinvention. FIG. 1B is a cross-sectional view taken along line X-X′ ofFIG. 1A. FIG. 1C is a cross-sectional view taken along line Y-Y′ of FIG.1A.

FIG. 2A is a plan view of a memory device according to the presentinvention. FIG. 2B is a cross-sectional view taken along line X-X′ ofFIG. 2A. FIG. 2C is a cross-sectional view taken along line Y-Y′ of FIG.2A.

FIG. 3A is a plan view of a memory device according to the presentinvention. FIG. 3B is a cross-sectional view taken along line X-X′ ofFIG. 3A. FIG. 3C is a cross-sectional view taken along line Y-Y′ of FIG.3A.

FIG. 4A is a plan view of a memory device according to the presentinvention. FIG. 4B is a cross-sectional view taken along line X-X′ ofFIG. 4A. FIG. 4C is a cross-sectional view taken along line Y-Y′ of FIG.4A.

FIG. 5A is a plan view illustrating a method for producing a memorydevice according to the present invention. FIG. 5B is a cross-sectionalview taken along line X-X′ of FIG. 5A. FIG. 5C is a cross-sectional viewtaken along line Y-Y′ of FIG. 5A.

FIG. 6A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 6B is a cross-sectionalview taken along line X-X′ of FIG. 6A. FIG. 6C is a cross-sectional viewtaken along line Y-Y′ of FIG. 6A.

FIG. 7A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 7B is a cross-sectionalview taken along line X-X′ of FIG. 7A. FIG. 7C is a cross-sectional viewtaken along line Y-Y′ of FIG. 7A.

FIG. 8A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 8B is a cross-sectionalview taken along line X-X′ of FIG. 8A. FIG. 8C is a cross-sectional viewtaken along line Y-Y′ of FIG. 8A.

FIG. 9A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 9B is a cross-sectionalview taken along line X-X′ of FIG. 9A. FIG. 9C is a cross-sectional viewtaken along line Y-Y′ of FIG. 9A.

FIG. 10A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 10B is a cross-sectionalview taken along line X-X′ of FIG. 10A. FIG. 10C is a cross-sectionalview taken along line Y-Y′ of FIG. 10A.

FIG. 11A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 11B is a cross-sectionalview taken along line X-X′ of FIG. 11A. FIG. 11C is a cross-sectionalview taken along line Y-Y′ of FIG. 11A.

FIG. 12A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 12B is a cross-sectionalview taken along line X-X′ of FIG. 12A. FIG. 12C is a cross-sectionalview taken along line Y-Y′ of FIG. 12A.

FIG. 13A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 13B is a cross-sectionalview taken along line X-X′ of FIG. 13A. FIG. 13C is a cross-sectionalview taken along line Y-Y′ of FIG. 13A.

FIG. 14A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 14B is a cross-sectionalview taken along line X-X′ of FIG. 14A. FIG. 14C is a cross-sectionalview taken along line Y-Y′ of FIG. 14A.

FIG. 15A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 15B is a cross-sectionalview taken along line X-X′ of FIG. 15A. FIG. 15C is a cross-sectionalview taken along line Y-Y′ of FIG. 15A.

FIG. 16A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 16B is a cross-sectionalview taken along line X-X′ of FIG. 16A. FIG. 16C is a cross-sectionalview taken along line Y-Y′ of FIG. 16A.

FIG. 17A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 17B is a cross-sectionalview taken along line X-X′ of FIG. 17A. FIG. 17C is a cross-sectionalview taken along line Y-Y′ of FIG. 17A.

FIG. 18A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 18B is a cross-sectionalview taken along line X-X′ of FIG. 18A. FIG. 18C is a cross-sectionalview taken along line Y-Y′ of FIG. 18A.

FIG. 19A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 19B is a cross-sectionalview taken along line X-X′ of FIG. 19A. FIG. 19C is a cross-sectionalview taken along line Y-Y′ of FIG. 19A.

FIG. 20A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 20B is a cross-sectionalview taken along line X-X′ of FIG. 20A. FIG. 20C is a cross-sectionalview taken along line Y-Y′ of FIG. 20A.

FIG. 21A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 21B is a cross-sectionalview taken along line X-X′ of FIG. 21A. FIG. 21C is a cross-sectionalview taken along line Y-Y′ of FIG. 21A.

FIG. 22A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 22B is a cross-sectionalview taken along line X-X′ of FIG. 22A. FIG. 22C is a cross-sectionalview taken along line Y-Y′ of FIG. 22A.

FIG. 23A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 23B is a cross-sectionalview taken along line X-X′ of FIG. 23A. FIG. 23C is a cross-sectionalview taken along line Y-Y′ of FIG. 23A.

FIG. 24A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 24B is a cross-sectionalview taken along line X-X′ of FIG. 24A. FIG. 24C is a cross-sectionalview taken along line Y-Y′ of FIG. 24A.

FIG. 25A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 25B is a cross-sectionalview taken along line X-X′ of FIG. 25A. FIG. 25C is a cross-sectionalview taken along line Y-Y′ of FIG. 25A.

FIG. 26A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 26B is a cross-sectionalview taken along line X-X′ of FIG. 26A. FIG. 26C is a cross-sectionalview taken along line Y-Y′ of FIG. 26A.

FIG. 27A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 27B is a cross-sectionalview taken along line X-X′ of FIG. 27A. FIG. 27C is a cross-sectionalview taken along line Y-Y′ of FIG. 27A.

FIG. 28A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 28B is a cross-sectionalview taken along line X-X′ of FIG. 28A. FIG. 28C is a cross-sectionalview taken along line Y-Y′ of FIG. 28A.

FIG. 29A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 29B is a cross-sectionalview taken along line X-X′ of FIG. 29A. FIG. 29C is a cross-sectionalview taken along line Y-Y′ of FIG. 29A.

FIG. 30A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 30B is a cross-sectionalview taken along line X-X′ of FIG. 30A. FIG. 30C is a cross-sectionalview taken along line Y-Y′ of FIG. 30A.

FIG. 31A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 31B is a cross-sectionalview taken along line X-X′ of FIG. 31A. FIG. 31C is a cross-sectionalview taken along line Y-Y′ of FIG. 31A.

FIG. 32A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 32B is a cross-sectionalview taken along line X-X′ of FIG. 32A. FIG. 32C is a cross-sectionalview taken along line Y-Y′ of FIG. 32A.

FIG. 33A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 33B is a cross-sectionalview taken along line X-X′ of FIG. 33A. FIG. 33C is a cross-sectionalview taken along line Y-Y′ of FIG. 33A.

FIG. 34A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 34B is a cross-sectionalview taken along line X-X′ of FIG. 34A. FIG. 34C is a cross-sectionalview taken along line Y-Y′ of FIG. 34A.

FIG. 35A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 35B is a cross-sectionalview taken along line X-X′ of FIG. 35A. FIG. 35C is a cross-sectionalview taken along line Y-Y′ of FIG. 35A.

FIG. 36A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 36B is a cross-sectionalview taken along line X-X′ of FIG. 36A. FIG. 36C is a cross-sectionalview taken along line Y-Y′ of FIG. 36A.

FIG. 37A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 37B is a cross-sectionalview taken along line X-X′ of FIG. 37A. FIG. 37C is a cross-sectionalview taken along line Y-Y′ of FIG. 37A.

FIG. 38A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 38B is a cross-sectionalview taken along line X-X′ of FIG. 38A. FIG. 38C is a cross-sectionalview taken along line Y-Y′ of FIG. 38A.

FIG. 39A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 39B is a cross-sectionalview taken along line X-X′ of FIG. 39A. FIG. 39C is a cross-sectionalview taken along line Y-Y′ of FIG. 39A.

FIG. 40A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 40B is a cross-sectionalview taken along line X-X′ of FIG. 40A. FIG. 40C is a cross-sectionalview taken along line Y-Y′ of FIG. 40A.

FIG. 41A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 41B is a cross-sectionalview taken along line X-X′ of FIG. 41A. FIG. 41C is a cross-sectionalview taken along line Y-Y′ of FIG. 41A.

FIG. 42A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 42B is a cross-sectionalview taken along line X-X′ of FIG. 42A. FIG. 42C is a cross-sectionalview taken along line Y-Y′ of FIG. 42A.

FIG. 43A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 43B is a cross-sectionalview taken along line X-X′ of FIG. 43A. FIG. 43C is a cross-sectionalview taken along line Y-Y′ of FIG. 43A.

FIG. 44A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 44B is a cross-sectionalview taken along line X-X′ of FIG. 44A. FIG. 44C is a cross-sectionalview taken along line Y-Y′ of FIG. 44A.

FIG. 45A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 45B is a cross-sectionalview taken along line X-X′ of FIG. 45A. FIG. 45C is a cross-sectionalview taken along line Y-Y′ of FIG. 45A.

FIG. 46A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 46B is a cross-sectionalview taken along line X-X′ of FIG. 46A. FIG. 46C is a cross-sectionalview taken along line Y-Y′ of FIG. 46A.

FIG. 47A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 47B is a cross-sectionalview taken along line X-X′ of FIG. 47A. FIG. 47C is a cross-sectionalview taken along line Y-Y′ of FIG. 47A.

FIG. 48A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 48B is a cross-sectionalview taken along line X-X′ of FIG. 48A. FIG. 48C is a cross-sectionalview taken along line Y-Y′ of FIG. 48A.

FIG. 49A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 49B is a cross-sectionalview taken along line X-X′ of FIG. 49A. FIG. 49C is a cross-sectionalview taken along line Y-Y′ of FIG. 49A.

FIG. 50A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 50B is a cross-sectionalview taken along line X-X′ of FIG. 50A. FIG. 50C is a cross-sectionalview taken along line Y-Y′ of FIG. 50A.

FIG. 51A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 51B is a cross-sectionalview taken along line X-X′ of FIG. 51A. FIG. 51C is a cross-sectionalview taken along line Y-Y′ of FIG. 51A.

FIG. 52A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 52B is a cross-sectionalview taken along line X-X′ of FIG. 52A. FIG. 52C is a cross-sectionalview taken along line Y-Y′ of FIG. 52A.

FIG. 53A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 53B is a cross-sectionalview taken along line X-X′ of FIG. 53A. FIG. 53C is a cross-sectionalview taken along line Y-Y′ of FIG. 53A.

FIG. 54A is a plan view illustrating the method for producing a memorydevice according to the present invention. FIG. 54B is a cross-sectionalview taken along line X-X′ of FIG. 54A. FIG. 54C is a cross-sectionalview taken along line Y-Y′ of FIG. 54A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A, 1B and 1C illustrate a structure of a memory device.

The memory device includes a pillar-shaped layer 501 whose resistancechanges, a reset gate insulating film 502 surrounding the pillar-shapedlayer 501 whose resistance changes, and a reset gate 503 surrounding thereset gate insulating film 502.

The pillar-shaped layer 501 whose resistance changes is preferablycomposed of chalcogenide glass (GST: Ge₂Sb₂Te₅).

A lower electrode 504 is provided under the pillar-shaped layer 501whose resistance changes.

The reset gate 503 may be composed of any material that generates heatwhen a current flows therein. The reset gate 503 is preferably composedof titanium nitride.

The reset gate insulating film 502 may be any insulating film havinggood thermal conductivity. The reset gate insulating film 502 ispreferably formed of a nitride film.

The lower electrode 504 may be composed of any material that generatesheat when a current flows therein. The lower electrode 504 is preferablycomposed of titanium nitride.

By allowing a current to flow in the reset gate 503, heat is generatedin the reset gate 503, which functions as a heater, and thepillar-shaped layer 501 whose resistance changes, the pillar-shapedlayer 501 contacting this heater, is melted and a transition of thestate of the pillar-shaped layer 501 can be caused.

In FIGS. 2A, 2B and 2C, a memory cell, which is a semiconductor deviceof the present invention, is arranged in each of the first column of thefirst row, the third column of the first row, the first column of thesecond row, and the third column of the second row. Furthermore, inorder to connect source lines to each other, a contact device includinga contact electrode and a contact line is arranged in the second columnof the first row and the second column of the second row.

The memory cell in the first column of the second row includes afin-shaped semiconductor layer 104 formed on a semiconductor substrate101, a first insulating film 106 formed around the fin-shapedsemiconductor layer 104, and a first pillar-shaped semiconductor layer129 formed on the fin-shaped semiconductor layer 104. A width of thefirst pillar-shaped semiconductor layer 129 in a direction perpendicularto a direction in which the fin-shaped semiconductor layer 104 extendsis the same as a width of the fin-shaped semiconductor layer 104 in thedirection perpendicular to the direction in which the fin-shapedsemiconductor layer 104 extends. Furthermore, the memory cell in thefirst column of the second row includes the first pillar-shapedsemiconductor layer 129, a gate insulating film 162 formed around thefirst pillar-shaped semiconductor layer 129, a gate electrode 168 acomposed of a metal and formed around the gate insulating film 162, agate line 168 b composed of a metal and connected to the gate electrode168 a, and the gate insulating film 162 formed on a periphery and abottom portion of the gate electrode 168 a and the gate line 168 b. Thegate line 168 b extends in the direction perpendicular to the directionin which the fin-shaped semiconductor layer 104 extends. The gateelectrode 168 a has an outer width the same as a width of the gate line168 b. Furthermore, the memory cell in the first column of the secondrow includes a first diffusion layer 302 formed in an upper portion ofthe first pillar-shaped semiconductor layer 129 and a second diffusionlayer 143 a formed in a lower portion of the first pillar-shapedsemiconductor layer 129. The second diffusion layer 143 a is furtherformed in the fin-shaped semiconductor layer 104.

A lower electrode 175 a, a pillar-shaped layer 176 a whose resistancechanges, a reset gate insulating film 182, and a reset gate 183 a aredisposed on the first diffusion layer 302.

The memory cell in the third column of the second row includes thefin-shaped semiconductor layer 104 formed on the semiconductor substrate101, the first insulating film 106 formed around the fin-shapedsemiconductor layer 104, and a first pillar-shaped semiconductor layer131 formed on the fin-shaped semiconductor layer 104. A width of thefirst pillar-shaped semiconductor layer 131 in a direction perpendicularto the direction in which the fin-shaped semiconductor layer 104 extendsis the same as a width of the fin-shaped semiconductor layer 104 in thedirection perpendicular to the direction in which the fin-shapedsemiconductor layer 104 extends. Furthermore, the memory cell in thethird column of the second row includes the first pillar-shapedsemiconductor layer 131, a gate insulating film 163 formed around thefirst pillar-shaped semiconductor layer 131, a gate electrode 170 acomposed of a metal and formed around the gate insulating film 163, agate line 170 b composed of a metal and connected to the gate electrode170 a, and the gate insulating film 163 formed on a periphery and abottom portion of the gate electrode 170 a and the gate line 170 b. Thegate line 170 b extends in the direction perpendicular to the directionin which the fin-shaped semiconductor layer 104 extends. The gateelectrode 170 a has an outer width the same as a width of the gate line170 b. Furthermore, the memory cell in the third column of the secondrow includes a first diffusion layer 304 formed in an upper portion ofthe first pillar-shaped semiconductor layer 131, and the seconddiffusion layer 143 a formed in a lower portion of the firstpillar-shaped semiconductor layer 131. The second diffusion layer 143 ais further formed in the fin-shaped semiconductor layer 104.

A lower electrode 175 b, a pillar-shaped layer 176 b whose resistancechanges, the reset gate insulating film 182, and a reset gate 183 b aredisposed on the first diffusion layer 304.

An upper portion of the pillar-shaped layer 176 a whose resistancechanges and an upper portion of the pillar-shaped layer 176 b whoseresistance changes are connected by a bit line 188 a.

The memory cell in the first column of the first row includes afin-shaped semiconductor layer 105 formed on the semiconductor substrate101, the first insulating film 106 formed around the fin-shapedsemiconductor layer 105, and a first pillar-shaped semiconductor layer132 formed on the fin-shaped semiconductor layer 105. A width of thefirst pillar-shaped semiconductor layer 132 in a direction perpendicularto a direction in which the fin-shaped semiconductor layer 105 extendsis the same as a width of the fin-shaped semiconductor layer 105 in thedirection perpendicular to the direction in which the fin-shapedsemiconductor layer 105 extends. Furthermore, the memory cell in thefirst column of the first row includes the first pillar-shapedsemiconductor layer 132, the gate insulating film 162 formed around thefirst pillar-shaped semiconductor layer 132, the gate electrode 168 acomposed of the metal and formed around the gate insulating film 162,the gate line 168 b composed of the metal and connected to the gateelectrode 168 a, and the gate insulating film 162 formed on a peripheryand a bottom portion of the gate electrode 168 a and the gate line 168b. The gate line 168 b extends in the direction perpendicular to thedirection in which the fin-shaped semiconductor layer 105 extends. Thegate electrode 168 a has an outer width the same as a width of the gateline 168 b. Furthermore, the memory cell in the first column of thefirst row includes a first diffusion layer 305 formed in an upperportion of the first pillar-shaped semiconductor layer 132, and a seconddiffusion layer 143 b formed in a lower portion of the firstpillar-shaped semiconductor layer 132. The second diffusion layer 143 bis further formed in the fin-shaped semiconductor layer 105.

A lower electrode 175 c, a pillar-shaped layer 176 c whose resistancechanges, the reset gate insulating film 182, and the reset gate 183 aare disposed on the first diffusion layer 305.

The memory cell in the third column of the first row includes thefin-shaped semiconductor layer 105 formed on the semiconductor substrate101, the first insulating film 106 formed around the fin-shapedsemiconductor layer 105, and a first pillar-shaped semiconductor layer134 formed on the fin-shaped semiconductor layer 105. A width of thefirst pillar-shaped semiconductor layer 134 in a direction perpendicularto the direction in which the fin-shaped semiconductor layer 105 extendsis the same as a width of the fin-shaped semiconductor layer 105 in thedirection perpendicular to the direction in which the fin-shapedsemiconductor layer 105 extends. Furthermore, the memory cell in thethird column of the first row includes the first pillar-shapedsemiconductor layer 134, the gate insulating film 163 formed around thefirst pillar-shaped semiconductor layer 134, the gate electrode 170 acomposed of the metal and formed around the gate insulating film 163,the gate line 170 b composed of the metal and connected to the gateelectrode 170 a, and the gate insulating film 163 formed on a peripheryand a bottom portion of the gate electrode 170 a and the gate line 170b. The gate line 170 b extends in the direction perpendicular to thedirection in which the fin-shaped semiconductor layer 105 extends. Thegate electrode 170 a has an outer width the same as a width of the gateline 170 b. Furthermore, the memory cell in the third column of thefirst row includes a first diffusion layer 307 formed in an upperportion of the first pillar-shaped semiconductor layer 134, and thesecond diffusion layer 143 b formed in a lower portion of the firstpillar-shaped semiconductor layer 134. The second diffusion layer 143 bis further formed in the fin-shaped semiconductor layer 105.

A lower electrode 175 d, a pillar-shaped layer 176 d whose resistancechanges, the reset gate insulating film 182, and the reset gate 183 bare disposed on the first diffusion layer 307.

The pillar-shaped layer 176 c whose resistance changes and thepillar-shaped layer 176 d whose resistance changes are connected by abit line 188 b.

The gate electrodes 168 a and 170 a are composed of a metal, and thegate lines 168 b and 170 b are composed of a metal. Thus, cooling can beaccelerated. In addition, the gate lines 168 b and 170 b that arerespectively formed on peripheries and bottom portions of the gateelectrodes 168 a and 170 a and the gate lines are provided. Accordingly,metal gates are formed by a gate-last process. Thus, a metal gateprocess and a high-temperature process can be combined.

The gate insulating films 162 and 163 that are respectively formed onperipheries and bottom portions of the gate electrodes 168 a and 170 aand the gate lines 168 b and 170 b are provided. The gate electrodes 168a and 170 a are composed of a metal, and the gate lines 168 b and 170 bare composed of a metal. The gate line 168 b and 170 b extend in thedirection perpendicular to the direction in which the fin-shapedsemiconductor layers 104 and 105 extend. The second diffusion layers 143a and 143 b are further formed in the fin-shaped semiconductor layers104 and 105, respectively. The outer widths of the gate electrodes 168 aand 170 a are the same as the width of the gate lines 168 b and 170 b,respectively. The widths of the first pillar-shaped semiconductor layers129, 131, 132, and 134 are the same as the widths of the fin-shapedsemiconductor layers 104 and 105. With this structure, the fin-shapedsemiconductor layers 104 and 105, the first pillar-shaped semiconductorlayers 129, 131, 132, and 134, the gate electrodes 168 a and 170 a, andthe gate lines 168 b and 170 b of the semiconductor device are formed byself-alignment using two masks. Thus, the number of steps can bereduced.

The contact device in the second column of the second row includes thefin-shaped semiconductor layer 104 formed on the semiconductor substrate101, the first insulating film 106 formed around the fin-shapedsemiconductor layer 104, and a second pillar-shaped semiconductor layer130 formed on the fin-shaped semiconductor layer 104. A width of thesecond pillar-shaped semiconductor layer 130 in a directionperpendicular to the direction in which the fin-shaped semiconductorlayer 104 extends is the same as a width of the fin-shaped semiconductorlayer 104 in the direction perpendicular to the direction in which thefin-shaped semiconductor layer 104 extends. Furthermore, the contactdevice in the second column of the second row includes a contactelectrode 169 a composed of a metal and formed around the secondpillar-shaped semiconductor layer 130, a gate insulating film 165 formedbetween the second pillar-shaped semiconductor layer 130 and the contactelectrode 169 a, a contact line 169 b composed of a metal extending in adirection perpendicular to the direction in which the fin-shapedsemiconductor layer 104 extends and connected to the contact electrode169 a, and a gate insulating film 164 formed on a periphery of thecontact electrode 169 a and the contact line 169 b. The contactelectrode 169 a has an outer width the same as a width of the contactline 169 b. Furthermore, the contact device in the second column of thesecond row includes a second diffusion layer 143 a formed in thefin-shaped semiconductor layer 104 and in a lower portion of the secondpillar-shaped semiconductor layer 130. The contact electrode 169 a isconnected to the second diffusion layer 143 a.

The contact device in the second column of the first row includes thefin-shaped semiconductor layer 105 formed on the semiconductor substrate101, the first insulating film 106 formed around the fin-shapedsemiconductor layer 105, and a second pillar-shaped semiconductor layer133 formed on the fin-shaped semiconductor layer 105. A width of thesecond pillar-shaped semiconductor layer 133 in a directionperpendicular to the direction in which the fin-shaped semiconductorlayer 105 extends is the same as a width of the fin-shaped semiconductorlayer 105 in the direction perpendicular to the direction in which thefin-shaped semiconductor layer 105 extends. Furthermore, the contactdevice in the second column of the first row includes the contactelectrode 169 a composed of the metal and formed around the secondpillar-shaped semiconductor layer 133, a gate insulating film 166 formedbetween the second pillar-shaped semiconductor layer 133 and the contactelectrode 169 a, the contact line 169 b composed of the metal extendingin a direction perpendicular to the direction in which the fin-shapedsemiconductor layer 105 extends and connected to the contact electrode169 a, and the gate insulating film 164 formed on a periphery of thecontact electrode 169 a and the contact line 169 b. The contactelectrode 169 a has an outer width the same as a width of the contactline 169 b. Furthermore, the contact device in the second column of thefirst row includes the second diffusion layer 143 b formed in thefin-shaped semiconductor layer 105 and in a lower portion of the secondpillar-shaped semiconductor layer 133. The contact electrode 169 a isconnected to the second diffusion layer 143 b.

By providing the contact line 169 b parallel to the gate lines 168 b and170 b and connected to the second diffusion layers 143 a and 143 b, thesecond diffusion layers 143 a and 143 b are connected to each other.With this structure, the resistance of a source line can be decreased,and an increase in the source voltage due to a current at the time ofthe setting can be suppressed. For example, one contact line 169 bparallel to the gate lines 168 b and 170 b is preferably arranged forevery two memory cells, every four memory cells, every eight memorycells, every sixteen memory cells, every thirty-two memory cells, orevery sixty-four memory cells that are arranged in a line in thedirection of the bit lines 188 a and 188 b.

The structure formed by the second pillar-shaped semiconductor layers130 and 133, the contact electrode 169 a that is formed around thesecond pillar-shaped semiconductor layers 130 and 133, and the contactline 169 b is the same as a transistor structure except that the contactelectrode 169 a is connected to the second diffusion layers 143 a and143 b. All the source lines formed of the second diffusion layers 143 aand 143 b in a direction parallel to the gate lines 168 b and 170 b areconnected to the contact line 169 b. Thus, the number of steps can bereduced.

FIGS. 3A, 3B and 3C illustrate a structure in which a second diffusionlayer 143 c is deeply formed in a semiconductor substrate 101 so thatthe second diffusion layers 143 a and 143 b in FIGS. 1A, 1B and 1C areconnected to each other. With this structure, the source resistance canbe further reduced.

FIGS. 4A, 4B and 4C illustrate a structure in which the fin-shapedsemiconductor layer 105 in FIGS. 2A, 2B and 2C and the first insulatingfilm 106 formed around the fin-shaped semiconductor layer 105 areomitted and a second diffusion layer 143 d is formed on a semiconductorsubstrate 101. With this structure, the source resistance can be furtherreduced.

A production process for forming the structure of a semiconductor deviceaccording to an embodiment of the present invention will now bedescribed with reference to FIGS. 5A to 54C.

First, a first step of forming a fin-shaped semiconductor layer on asemiconductor substrate and forming a first insulating film around thefin-shaped semiconductor layer will be described. In the presentembodiment, a silicon substrate is used. However, any semiconductor maybe used.

As illustrated in FIGS. 5A, 5B and 5C, a first resists 102 and 103 forforming fin-shaped silicon layers are formed on a silicon substrate 101.

As illustrated in FIGS. 6A, 6B and 6C, the silicon substrate 101 isetched to form fin-shaped silicon layers 104 and 105. In the presentembodiment, the fin-shaped silicon layers are formed by using a resistas a mask. Alternatively, a hard mask such as an oxide film or a nitridefilm may be used.

As illustrated in FIGS. 7A, 7B and 7C, the first resists 102 and 103 areremoved.

As illustrated in FIGS. 8A, 8B and 8C, a first insulating film 106 isdeposited around the fin-shaped silicon layers 104 and 105. An oxidefilm formed by high-density plasma or an oxide film formed bylow-pressure chemical vapor deposition (CVD) may be used as the firstinsulating film.

As illustrated in FIGS. 9A, 9B and 9C, a first insulating film 106 isetched back to expose upper portions of the fin-shaped silicon layers104 and 105.

The first step of forming a fin-shaped semiconductor layer on asemiconductor substrate and forming a first insulating film around thefin-shaped semiconductor layer has been described.

Next, a description will be made of a second step of, after the firststep, forming a second insulating film around the fin-shapedsemiconductor layer, depositing a first polysilicon on the secondinsulating film and planarizing the first polysilicon, forming a secondresist for forming a gate line, a first pillar-shaped semiconductorlayer, a second pillar-shaped semiconductor layer, and a contact line ina direction perpendicular to a direction in which the fin-shapedsemiconductor layer extends, and etching the first polysilicon, thesecond insulating film, and the fin-shaped semiconductor layer tothereby form a first pillar-shaped semiconductor layer, a first dummygate composed of the first polysilicon, a second pillar-shapedsemiconductor layer, and a second dummy gate composed of the firstpolysilicon.

As illustrated in FIGS. 10A, 10B and 10C, second insulating films 107and 108 are formed around the fin-shaped silicon layers 104 and 105,respectively. The second insulating films 107 and 108 are preferablyoxide films.

As illustrated in FIGS. 11A, 11B and 1C, a first polysilicon 109 isdeposited on the second insulating films 107 and 108 and planarizing thefirst polysilicon 109.

As illustrated in FIGS. 12A, 12B and 12C, a third insulating film 110 isformed on the first polysilicon 109. The third insulating film 110 ispreferably a nitride film.

As illustrated in FIGS. 13A, 13B and 13C, second resists 111, 112, and113 for forming gate lines 168 b and 170 b, first pillar-shapedsemiconductor layers 129, 131, 132, and 134, second pillar-shapedsemiconductor layers 130 and 133, and a contact line 169 b are formed ina direction perpendicular to a direction in which the fin-shaped siliconlayers 104 and 105 extend.

As illustrated in FIGS. 14A, 14B and 14C, the third insulating film 110,the first polysilicon 109, the second insulating films 107 and 108, andthe fin-shaped silicon layers 104 and 105 are etched to thereby formfirst pillar-shaped silicon layers 129, 131, 132, and 134, first dummygates 117 and 119 composed of the first polysilicon, secondpillar-shaped silicon layers 130 and 133, and a second dummy gate 118composed of the first polysilicon. At this time, the third insulatingfilm 110 is separated into third insulating films 114, 115, and 116. Thesecond insulating films 107 and 108 are separated into second insulatingfilms 123, 124, 125, 126, 127, and 128. At this time, in the case wherethe second resists 111, 112, and 113 are removed during the etching, thethird insulating films 114, 115, and 116 function as a hard mask. In thecase where the second resists are not removed during the etching, thethird insulating film may not be used.

As illustrated in FIGS. 15A, 15B and 15C, the third insulating films114, 115, and 116 are removed.

A description has been made of the second step of, after the first step,forming a second insulating film around the fin-shaped semiconductorlayer, depositing a first polysilicon on the second insulating film andplanarizing the first polysilicon, forming a second resist for forming agate line, a first pillar-shaped semiconductor layer, a secondpillar-shaped semiconductor layer, and a contact line in a directionperpendicular to a direction in which the fin-shaped semiconductor layerextends, and etching the first polysilicon, the second insulating film,and the fin-shaped semiconductor layer to thereby form a firstpillar-shaped semiconductor layer, a first dummy gate composed of thefirst polysilicon, a second pillar-shaped semiconductor layer, and asecond dummy gate composed of the first polysilicon.

Next, a description will be made of a third step of, after the secondstep, forming a fourth insulating film around the first pillar-shapedsemiconductor layer, the second pillar-shaped semiconductor layer, thefirst dummy gate, and the second dummy gate, depositing a secondpolysilicon around the fourth insulating film, and leaving, byconducting etching, the second polysilicon on side walls of the firstdummy gate, the first pillar-shaped semiconductor layer, the seconddummy gate, and the second pillar-shaped semiconductor layer to form athird dummy gate and a fourth dummy gate.

As illustrated in FIGS. 16A, 16B and 16C, a fourth insulating film 135is formed around the first pillar-shaped silicon layers 129, 131, 132,and 134, the second pillar-shaped silicon layers 130 and 133, the firstdummy gates 117 and 119, and the second dummy gate 118. The fourthinsulating film 135 is preferably an oxide film. A third resist 301 isformed, and etch-back is then performed to expose upper portions of thefirst pillar-shaped silicon layers 129, 131, 132, and 134. At this time,upper portions of the second pillar-shaped silicon layers 130 and 133may be exposed.

As illustrated in FIGS. 17A, 17B and 17C, an impurity is introduced toform first diffusion layers 302, 304, 305, and 307 in upper portions ofthe first pillar-shaped silicon layers 129, 131, 132, and 134,respectively. First diffusion layers 303 and 306 may be formed in upperportions of the second pillar-shaped silicon layers 130 and 133,respectively. In the case of an n-type diffusion layer, arsenic orphosphorus is preferably introduced. In the case of a p-type diffusionlayer, boron is preferably introduced.

As illustrated in FIGS. 18A, 18B and 18C, the third resist 301 isremoved.

As illustrated in FIGS. 19A, 19B and 19C, a second polysilicon 136 isdeposited around the fourth insulating film 135.

As illustrated in FIGS. 20A, 20B and 20C, by etching the secondpolysilicon 136, the second polysilicon 136 is left on side walls of thefirst dummy gates 117 and 119, the first pillar-shaped silicon layers129, 131, 132, and 134, the second dummy gate 118, and the secondpillar-shaped silicon layers 130 and 133. Thus, third dummy gates 137and 139 and a fourth dummy gate 138 are formed. At this time, the fourthinsulating film 135 may be separated into fourth insulating films 140,141, and 142.

A description has been made of the third step of, after the second step,forming a fourth insulating film around the first pillar-shapedsemiconductor layer, the second pillar-shaped semiconductor layer, thefirst dummy gate, and the second dummy gate, depositing a secondpolysilicon around the fourth insulating film, and leaving, byconducting etching, the second polysilicon on side walls of the firstdummy gate, the first pillar-shaped semiconductor layer, the seconddummy gate, and the second pillar-shaped semiconductor layer to form athird dummy gate and a fourth dummy gate.

Next, a description will be made of a fourth step of forming a seconddiffusion layer in an upper portion of the fin-shaped semiconductorlayer, in a lower portion of the first pillar-shaped semiconductorlayer, and in a lower portion of the second pillar-shaped semiconductorlayer, forming a fifth insulating film around the third dummy gate andthe fourth dummy gate, leaving the fifth insulating film in a side wallshape by etching to form side walls formed of the fifth insulating film,and forming a compound of a metal and a semiconductor in an upperportion of the second diffusion layer.

As illustrated in FIGS. 21A, 21B and 21C, an impurity is introduced toform second diffusion layers 143 a and 143 b in lower portions of thefirst pillar-shaped silicon layers 129, 131, 132, and 134 and in lowerportions of the second pillar-shaped silicon layers 130 and 133. In thecase of an n-type diffusion layer, arsenic or phosphorus is preferablyintroduced. In the case of a p-type diffusion layer, boron is preferablyintroduced. The diffusion layers may be formed after the formation ofside walls formed of a fifth insulating film described below.

As illustrated in FIGS. 22A, 22B and 22C, a fifth insulating film 144 isformed around the third dummy gates 137 and 139 and the fourth dummygate 138. The fifth insulating film 144 is preferably a nitride film.

As illustrated in FIGS. 23A, 23B and 23C, the fifth insulating film 144is etched so as to be left in a side wall shape, thereby forming sidewalls 145, 146, and 147 formed of the fifth insulating film.

As illustrated in FIGS. 24A, 24B and 24C, compounds 148, 149, 150, 151,152, 153, 154, and 155 of a metal and a semiconductor are formed inupper portions of the second diffusion layers 143 a and 143 b. At thistime, compounds 156, 158, and 157 of a metal and a semiconductor arealso formed in upper portions of the third dummy gates 137 and 139 andin an upper portion of the fourth dummy gate 138, respectively.

A description has been made of the fourth step of forming a seconddiffusion layer in an upper portion of the fin-shaped semiconductorlayer, in a lower portion of the first pillar-shaped semiconductorlayer, and in a lower portion of the second pillar-shaped semiconductorlayer, forming a fifth insulating film around the third dummy gate andthe fourth dummy gate, leaving the fifth insulating film in a side wallshape by etching to form side walls formed of the fifth insulating film,and forming a compound of a metal and a semiconductor in an upperportion of the second diffusion layer.

Next, a description will be made of a fifth step of after the fourthstep, depositing an interlayer insulating film and planarizing theinterlayer insulating film to expose upper portions of the first dummygate, the second dummy gate, the third dummy gate, and the fourth dummygate, removing the first dummy gate, the second dummy gate, the thirddummy gate, and the fourth dummy gate, removing the second insulatingfilm and the fourth insulating film, forming a gate insulating filmaround the first pillar-shaped semiconductor layer, around the secondpillar-shaped semiconductor layer, and on an inner side of the fifthinsulating film, forming a fourth resist for removing a portion of thegate insulating film which is located on a periphery of a bottom portionof the second pillar-shaped semiconductor layer, removing the portion ofthe gate insulating film which is located on the periphery of the bottomportion of the second pillar-shaped semiconductor layer, depositing ametal and etching back the metal to form a gate electrode and a gateline around the first pillar-shaped semiconductor layer and to form acontact electrode and a contact line around the second pillar-shapedsemiconductor layer.

As illustrated in FIGS. 25A, 25B and 25C, an interlayer insulating film159 is deposited. A contact stopper film may be used.

As illustrated in FIGS. 26A, 26B and 26C, upper portions of the firstdummy gates 117 and 119, the second dummy gate 118, the third dummygates 137 and 139, and the fourth dummy gate 138 are exposed by chemicalmechanical polishing. At this time, the compounds 156, 158, and 157 ofthe metal and the semiconductor in the upper portions of the third dummygates 137 and 139 and the upper portion of the fourth dummy gate 138 areremoved.

As illustrated in FIGS. 27A, 27B and 27C, the first dummy gates 117 and119, the second dummy gate 118, the third dummy gates 137 and 139, andthe fourth dummy gate 138 are removed.

As illustrated in FIGS. 28A, 28B and 28C, the second insulating films123, 124, 125, 126, 127, and 128 and the fourth insulating films 140,141, and 142 are removed.

As illustrated in FIGS. 29A, 29B and 29C, a gate insulating film 160 isformed around the first pillar-shaped silicon layers 129, 131, 132, and134, around the second pillar-shaped silicon layers 130 and 133, and oninner sides of the side walls 145, 146, and 147.

As illustrated in FIGS. 30A, 30B and 30C, a fourth resist 161 is formed.The fourth resist 161 is used for removing portions of the gateinsulating film 160 which are located on the periphery of bottomportions of the second pillar-shaped silicon layers 130 and 133.

As illustrated in FIGS. 31A, 31B and 31C, the portions of the gateinsulating film 160 which are located on the periphery of the bottomportions of the second pillar-shaped silicon layers 130 and 133 areremoved. The gate insulating film is separated into gate insulatingfilms 162, 163, 164, 165, and 166. The gate insulating films 164, 165,and 166 may be removed by isotropic etching.

As illustrated in FIGS. 32A, 32B and 32C, the fourth resist 161 isremoved.

As illustrated in FIGS. 33A, 33B and 33C, a metal 167 is deposited.

As illustrated in FIGS. 34A, 34B and 34C, the metal 167 is etched back.Thus, gate electrodes 168 a and 170 a and gate lines 168 b and 170 b areformed around the first pillar-shaped silicon layers 129, 131, 132, and134. A contact electrode 169 a and a contact line 169 b are formedaround the second pillar-shaped silicon layers 130 and 133.

A description has been made of the fifth step of, after the fourth step,depositing an interlayer insulating film and planarizing the interlayerinsulating film to expose upper portions of the first dummy gate, thesecond dummy gate, the third dummy gate, and the fourth dummy gate,removing the first dummy gate, the second dummy gate, the third dummygate, and the fourth dummy gate, removing the second insulating film andthe fourth insulating film, forming a gate insulating film around thefirst pillar-shaped semiconductor layer, around the second pillar-shapedsemiconductor layer, and on an inner side of the fifth insulating film,forming a fourth resist for removing a portion of the gate insulatingfilm which is located on a periphery of a bottom portion of the secondpillar-shaped semiconductor layer, removing the portion of the gateinsulating film which is located on the periphery of the bottom portionof the second pillar-shaped semiconductor layer, depositing a metal andetching back the metal to form a gate electrode and a gate line aroundthe first pillar-shaped semiconductor layer and to form a contactelectrode and a contact line around the second pillar-shapedsemiconductor layer.

Next, a description will be made of a sixth step of, after the fifthstep, depositing a second interlayer insulating film and planarizing thesecond interlayer insulating film to expose an upper portion of thefirst pillar-shaped semiconductor layer, forming a pillar-shaped layerwhose resistance changes and a lower electrode, forming a reset gateinsulating film so as to surround the pillar-shaped layer whoseresistance changes and the lower electrode, and forming a reset gate.

As illustrated in FIGS. 35A, 35B and 35C, a second interlayer insulatingfilm 171 is deposited.

As illustrated in FIGS. 36A, 36B and 36C, the second interlayerinsulating film 171 is etched back to expose upper portions of the firstpillar-shaped silicon layers 129, 131, 132, and 134 and upper portionsof the second pillar-shaped silicon layers 130 and 133.

As illustrated in FIGS. 37A, 37B and 37C, a metal 175 for lowerelectrodes, a film 176 whose resistance changes, and a nitride film 177are deposited.

As illustrated in FIGS. 38A, 38B and 38C, fifth resists 178, 179, 180,and 181 for forming pillar-shaped layers whose resistances change andlower electrodes are formed.

As illustrated in FIGS. 39A, 39B and 39C, the nitride film 177, the film176 whose resistance changes, and the metal 175 are etched. The nitridefilm 177 is separated into nitride films 177 a, 177 b, 177 c, and 177 d.The film 176 whose resistance changes is separated into pillar-shapedlayers 176 a, 176 b, 176 c, and 176 d whose resistances change. Themetal 175 is separated into lower electrodes 175 a, 175 b, 175 c, and175 d.

As illustrated in FIGS. 40A, 40B and 40C, the fifth resists 178, 179,180, and 181 are removed.

As illustrated in FIGS. 41A, 41B and 41C, a reset gate insulating film182 is deposited.

As illustrated in FIGS. 42A, 42B and 42C, a metal 183 which is to becomereset gates is deposited.

As illustrated in FIGS. 43A, 43B and 43C, the metal 183 is etched back.

As illustrated in FIGS. 44A, 44B and 44C, a nitride film 184 isdeposited.

As illustrated in FIGS. 45A, 45B and 45C, sixth resists 185 and 186 forforming reset gates are formed.

As illustrated in FIGS. 46A, 46B and 46C, the nitride film 184 isetched. The nitride film 184 is separated into nitride films 184 a and184 b.

As illustrated in FIGS. 47A, 47B and 47C, the metal 183 is etched byusing the sixth resists 185 and 186 and the nitride films 184 a and 184b as a mask to from reset gates 183 a and 183 b.

As illustrated in FIGS. 48A, 48B and 48C, the sixth resists 185 and 186are removed.

As illustrated in FIGS. 49A, 49B and 49C, a third interlayer insulatingfilm 187 is deposited.

As illustrated in FIGS. 50A, 50B and 50C, the third interlayerinsulating film 187 is planarized, and the nitride films 177 a, 177 b,177 c, and 177 d are removed so as to expose upper portions of thepillar-shaped layers 176 a, 176 b, 176 c, and 176 d whose resistanceschange.

As illustrated in FIGS. 51A, 51B and 51C, a metal 188 is deposited.

As illustrated in FIGS. 52A, 52B and 52C, seventh resists 189 and 190for forming bit lines are formed.

As illustrated in FIGS. 53A, 53B and 53C, the metal 188 is etched toform bit lines 188 a and 188 b.

As illustrated in FIGS. 54A, 54B and 54C, the seventh resists 189 and190 are removed.

A description has been made of the sixth step of, after the fifth step,depositing a second interlayer insulating film and planarizing thesecond interlayer insulating film to expose an upper portion of thefirst pillar-shaped semiconductor layer, forming a pillar-shaped layerwhose resistance changes and a lower electrode, forming a reset gateinsulating film so as to surround the pillar-shaped layer whoseresistance changes and the lower electrode, and forming a reset gate.

A production process for forming the structure of a memory deviceaccording to an embodiment of the present invention has been described.

It is to be understood that various embodiments and modifications of thepresent invention can be made without departing from the broad spiritand the scope of the present invention. The embodiments described aboveare illustrative examples of the present invention and do not limit thescope of the present invention.

For example, in the above embodiments, a method for producing asemiconductor device in which the conductivity types of the p type(including the p⁺ type) and the n type (including the n⁺ type) are eachchanged to the opposite conductivity type, and a semiconductor deviceproduced by the method are also included in the technical scope of thepresent invention.

The invention claimed is:
 1. A semiconductor device comprising: a firstpillar-shaped semiconductor layer; a gate insulating film around thefirst pillar-shaped semiconductor layer; a gate electrode around thegate insulating film; a gate line connected to the gate electrode; afirst diffusion layer in an upper portion of the first pillar-shapedsemiconductor layer; a second diffusion layer in a lower portion of thefirst pillar-shaped semiconductor layer; and a memory device on thefirst diffusion layer, the memory device including: a pillar-shapedphase-change layer; a reset gate insulating film surrounding thepillar-shaped phase-change layer; and a reset gate surrounding the resetgate insulating film, wherein the reset gate functions as a heater, andthe pillar-shaped phase-change layer and the reset gate are electricallyinsulated from each other.
 2. The semiconductor device according toclaim 1 further comprising: a fin-shaped semiconductor layer on asemiconductor substrate; and a first insulating film around thefin-shaped semiconductor layer, wherein the first pillar-shapedsemiconductor layer is on the fin-shaped semiconductor layer, the gateinsulating film is on a periphery and a bottom portion of the gateelectrode and the gate line, the gate electrode is composed of a metal,the gate line is composed of a metal, and the gate line extends in adirection perpendicular to a direction in which the fin-shapedsemiconductor layer extends, and the second diffusion layer furtherresides in the fin-shaped semiconductor layer.
 3. The semiconductordevice according to claim 2, wherein the second diffusion layer furtherresides in the semiconductor substrate.
 4. The semiconductor deviceaccording to claim 2 further comprising a contact line that is parallelto the gate line and connected to the second diffusion layer.
 5. Thesemiconductor device according to claim 4 further comprising: a secondpillar-shaped semiconductor layer on the fin-shaped semiconductor layer;a contact electrode around the second pillar-shaped semiconductor layerand composed of a metal; wherein the contact line is connected to thecontact electrode and composed of a metal extending in a directionperpendicular to the direction in which the fin-shaped semiconductorlayer extends, and the second diffusion layer is in a lower portion ofthe second pillar-shaped semiconductor layer, and the contact electrodeis connected to the second diffusion layer.
 6. The semiconductor deviceaccording to claim 5, wherein the gate insulating film further residesbetween the second pillar-shaped semiconductor layer and the contactelectrode.
 7. The semiconductor device according to claim 6 furthercomprising the gate insulating film formed on a periphery of the contactelectrode and the contact line.
 8. The semiconductor device according toclaim 5, wherein a width of the second pillar-shaped semiconductor layerin the direction perpendicular to the direction in which the fin-shapedsemiconductor layer extends is the same as the width of the fin-shapedsemiconductor layer in the direction perpendicular to the direction inwhich the fin-shaped semiconductor layer extends.
 9. The semiconductordevice according to claim 5, wherein an outer width of the contactelectrode is the same as a width of the contact line.
 10. Thesemiconductor device according to claim 2, wherein an outer width of thegate electrode is the same as a width of the gate line, and a width ofthe first pillar-shaped semiconductor layer in the directionperpendicular to the direction in which the fin-shaped semiconductorlayer extends is the same as a width of the fin-shaped semiconductorlayer in the direction perpendicular to the direction in which thefin-shaped semiconductor layer extends.
 11. The semiconductor deviceaccording to claim 1, wherein the first pillar-shaped semiconductorlayer is on a semiconductor substrate, the gate insulating film furtherresides on a periphery and a bottom portion of the gate electrode andthe gate line, the gate electrode is composed of a metal, the gate lineis composed of a metal, and the second diffusion layer is furtherresides in the semiconductor substrate.